For thousands of years, and perhaps even before the emergence of Homo sapiens, humans have altered their consciousness through the use of psychoactive botanicals. While most of these substances produce merely a mild mood­altering effect, a few have been found to trigger profound nonordinary states, which are inevitably imbued with religious significance by the cultures that employ them. The use of psychedelics for religious purposes can be traced to the classical civilizations of antiquity, such as in the Eleusinian Mysteries of the Greeks or the sacred soma used in Vedic rituals. Psychedelic botanicals have also been in continuous use as sacraments in indigenous cultures worldwide for centuries at least. The existence of such mind­altering psychedelic substances, however, was largely unknown to the culture of the developed world until early advocates of progressive spirituality began to extol the virtues of psychedelic experience.

Among the first progressive spiritual intellectuals to write about the mystical merits of psychedelic experience was Aldous Huxley, whose 1954 book The Doors of Perception introduced mescaline to a generation of curious spiritual seekers. Interest in substance­induced spiritual experience would later become widespread and highly visible in Western culture in the 1960s as the countercultural youth movement burst upon the scene. As a result of the zealous promotion of LSD and other psychedelics by Timothy Leary and others, these substances soon came to be regarded as a threat to the established social order and were eventually classified together with addictive narcotics as dangerous and illegal drugs. But despite the imposition of strict penalties for their use, these outlawed substances would nevertheless play an undeniable role in the emergence of progressive spirituality as a distinct form of spiritual culture. And having lived through this history myself, I can testify to the authentic spiritual significance of psychedelic experience.

Some knowledgeable writers on the subject, such as religious scholar Houston Smith, argue that the nonordinary states induced by psychedelics are largely identical to the classic categories of mysticism. In my experience, however, while there is some overlap between mystical and psychedelic states, the special quality and variety of psychedelic experience warrants its classification as a distinct form of spiritual experience.

Also, as with mystical experience, the spiritual content of psychedelic experience often serves as a kind of Rorschach test for one’s spiritual belief system. Such experiences are frequently interpreted in terms corresponding to a particular spiritual teaching about ultimate reality. But despite this tendency, I believe it is possible to use the common features of these experiences to broaden our understanding of the reality of spirit.

Mystical experiences have been overly universalized by commentators seeking to interpret a wide variety of distinct encounters with the transcendent as experiences of essentially the same thing. By contrast, psychedelic experiences have been overly particularized by claims that such experiences are unique for each person and highly susceptible to contextual influences, known as “set and setting.” Yet even though set and setting are important, the experiences produced by various psychedelic substances are relatively predictable and cross­culturally similar. And this commonality is reinforced by the fact that different psychedelic substances produce reliably distinct spiritual experiences, especially when such substances are taken with a sacramental intention.

For example, those who take a proper dose of ayahuasca (a brew made from two rainforest botanicals) inevitably embark on an inward journey of deep personal insight and discovery that frequently results in positive life changes. I can attest that after taking ayahuasca for the first time in 1994 I felt a little like Saint Francis of Assisi the next day. The experience left me with an extraordinary sense of love for each person in my life; I felt more free, more gentle, more reassured, and more open to the synchronistic assistance of larger spiritual forces that I could not understand but nevertheless knew were active in my life. Even though this elevated feeling wore off after a few days, the ayahuasca experience did in fact result in a “course correction” in my life that proved to be an important step in my personal spiritual development.

Now in my fifties, having practiced many forms of spirituality and having had a wide range of spiritual experiences going back to my youth, I can affirm that both natural and synthetic psychedelic substances are capable of producing intense encounters with undeniable spiritual realities. Although, as noted, different substances produce distinct experiences, most entheogens have a strong “noetic quality” that provides access to profound insights beyond the reach of normal cognition. In most cases, the onset of a psychedelic experience brings a palpable sense of cosmic consciousness in which the spiritual nature of the universe is almost laughably obvious. And even after coming down from the drug, the profundity of the insights and the conviction of having made contact with higher spiritual realms strongly remain. Indeed, I have found that every one of my psychedelic journeys has had a moral—a practical lesson seemingly tailored to my personal spiritual needs at the time.

Although beyond my personal experience, some users actually report psychological and even physical healing resulting from psychedelics. While I could certainly go on about the spiritual phenomenology of various psychedelic substances, suffice it to conclude that entheogens provide authentic and reliable access to undeniably spiritual experience. Yet if this is the case—if life­changing spiritual experience can be produced simply by altering our brain chemistry—then what does this mean for spiritual experience in general? Can spiritual experience be reduced to a neurological explanation?

Secularists and scientific materialists, of course, have a strong interest in denying or otherwise refuting the apparent metaphysical referent of every kind of spiritual experience. Freud, for example, categorized mystical experience as a remnant of the pre­separative ego state of infants. Other materialist authors have analyzed spiritual experience from the perspective of evolutionary psychology, arguing that the religious impulse is merely a functionalist mechanism that promotes group solidarity and thus species survival. Evolutionary psychology, however, is merely one of many strategies used by materialists to explain away spiritual experience as simply being “all in the head.” Over the last two decades this materialist explanation has been seemingly fortified by advances in brain­imaging technologies, such as PET, SPECT, and fMRI machines. These technologies have spurred a now­immense scientific project of discovering “the neural correlates of consciousness,” and many expect the findings of this research to eventually reduce the explanation of mental states of awareness to the electrical­chemical activity of the brain.

Using these techniques, some researchers have studied the brains of advanced meditators in an attempt to isolate or explain spiritual experience in purely neurophysiological terms. And I believe these investigations, sometimes called “neurotheology,” are certainly worthwhile. In fact, according to integral philosophy there is a strong connection between the interior and exterior (or mental and physical) dimensions of evolution, with the complexity of consciousness generally corresponding to the complexity of the brain it inhabits. So we would naturally expect to find many correlations between states of conscious awareness and brain states. However, such correlations do not provide grounds for gross reductionism. Indeed, the spiritual lessons of evolution clearly reveal how reductionism in all its forms is essentially false. This is shown by the very structure of emergence, wherein something more keeps coming from something less.

Just as life cannot be reduced to matter, conscious awareness—ordinary or nonordinary—cannot be reduced to brain states. According to philosopher Evan Thompson, neuroscience’s foundational assumption that the mind is in the brain is confused. “It’s like saying that flight is inside the wings of a bird. . . . You need a brain, just as the bird needs wings, but the mind exists at a different level.”1 Moreover, despite the loose correspondences that can be found between subjective consciousness and objective brain activity, the entire project of charting the neural correlates of consciousness is called into question by numerous, carefully documented near­death experiences demonstrating that consciousness and even perception can continue when the brain is effectively dead.

Interestingly, the idea that spiritual experience cannot be reduced to the brain may at first seem to be challenged by the case of psychedelic drugs, which appear to act as powerful triggers of such experiences merely by the ingestion of certain brain­altering chemicals. Researchers have found that psychedelic substances mimic the brain’s natural neurotransmitters, either blocking or releasing chemicals naturally produced by the brain, such as serotonin, dopamine, and norepinephrine. Different psychedelics result in distinct experiences by producing unique combinations of inhibition and release, altering the brain’s chemistry in a manner that can be compared to the playing of a musical instrument. Extending the analogy, we can see how each kind of entheogen plays a unique set of “chords on the keyboard” of the brain’s neurotransmitter receptor sites, which results in the distinct versions of psychedelic experience.2

Neurophysiologists who have never experienced a powerful psychedelic journey may be attracted to the reductionist implications of these chemical triggers of spiritual experience, but most of those who have actually had such experiences know better. That is, entheogens clearly reveal an expanded dimension of reality, and becoming aware of the very presence of such an enlarged reality serves as a spiritual teaching in itself. And despite some claims to the contrary, such experiences cannot be induced in their fullness through breath work, ecstatic dance, meditation, or other nonpharmacological techniques. This is why psychedelic spiritual experience must be recognized as a distinct category of its own and not merely a shortcut to classic mystical experiences better achieved through natural practices.

Initiation into the spiritual insights provided by entheogens reveals how we are truly “behind a veil” in our ordinary state of awareness. From the inside, the phenomenology of practically all psychedelic substances points to a conception of the brain not as a generator of consciousness itself, but as a filter or “reducing valve” limiting our perception of the larger reality that is all around us, so we can function in the everyday world. In fact, neuroscience may eventually show that the brain can be more accurately conceived as a receiver or “antenna” for consciousness rather than as an original generator of it.

Regarding the relationship between neurotheology and spiritual experience in general, it must be acknowledged that much of what we experience is clearly determined by our physiology. We are also determined to a great extent by the larger cultural structures we use to make meaning. But in between the deterministic influences of both our brains and our culture, we each have a small degree of freedom. And it is through this gift of freedom that we are privileged to serve as authentic agents of evolution.

The “chords on the keyboard” analogy is from Neal M. Goldsmith, Psychedelic Healing: The Promise of Entheogens for Psychotherapy and Spiritual Development (Rochester, VT: Healing Arts Press, 2011), 110.

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About the Author

Steve McIntosh is author of the books: The Presence of the Infinite (Quest 2015), Evolution’s Purpose (Select Books 2012), and Integral Consciousness (Paragon House 2007). In addition to his work in spiritual philosophy, he is also co-founder and president of the integral political think tank, The Institute for Cultural Evolution, which focuses on the cultural roots of America’s challenges. For more on his work visit: www.stevemcintosh.com